JPH0212263A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance photosensitivity and surface potential and to reduce residual potential by forming a specified amorphous silicon carbide photoconductive layer composed of first, second, and third layer regions laminated successively. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate 1 the a-SiC photoconductive layer 2 composed of the 3 layer regions 2a, 2b, 2c laminated successively, and an organic semiconductor layer 3. The first layer region 2a and the third layer region 2c contain more C than the layer region 2b, and have each an atomic composition Si1-xCx, where 0.2<x<0.5, and the region 2a has a thickness of 0.01-1mum, and the region 2b has a thickness of 0.05-5mum, and the region 2c has a thickness of 10-2,000Angstrom , thus permitting all the characteristics of photosensitivity, residual potential resistance, and surface potential to be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor comprising a laminated layer of an amorphous silicon carbide conductive layer and an organic optical semiconductor layer.

[Prior art and its problems]

Photoconductive materials for electrophotographic photoreceptors include Se, 5e-Te,
.

There are inorganic materials such as amorphous silicon and various organic materials. Among them, Se was the first to be put into practical use, and ZnO
, CdS, and amorphous silicon have also been put into practical use. On the other hand, among organic materials, PVK-TNF was first put into practical use, and later, a functionally separated photoreceptor was proposed in which the functions of charge generation and charge transport were shared between separate organic materials, and this functionally separated photoreceptor The development of organic materials is progressing dramatically.

On the other hand, an electrophotographic photoreceptor in which an organic photoconductive layer is laminated on the inorganic photoconductive layer has also been proposed.

For example, there is a laminated photoreceptor made of 5eWJ and an organic optical semiconductor layer, which has already been put into practical use, but this photoreceptor has the disadvantage that Se itself is harmful and has poor sensitivity on the long wavelength side.

Therefore, Japanese Unexamined Patent Publication No. 14241/1983 proposes a laminated photoconductor consisting of a 7-morphous silicon carbide photoconductive layer and an organic photoconductor layer, and this photoconductor solves the above problems. The properties of pollution-free property and high light sensitivity were obtained.

However, when the present inventors manufactured such an electrophotographic photoreceptor and measured its photosensitivity, residual potential, and surface potential, satisfactory characteristics were still not obtained, and further improvements are needed. It turned out that it required.

Therefore, the present invention has been completed in view of the above, and its object is to provide an electrophotographic photoreceptor that can improve all of the characteristics of photosensitivity, residual potential, and surface potential.

[Means for solving problems]

According to the present invention, amorphous silicon carbide photoconductive II! In an electrophotographic photoreceptor in which amorphous silicon carbide (amorphous silicon carbide is abbreviated as a-3iC hereinafter) and an organic photoconductive layer are sequentially laminated, the a-SiC photoconductive layer forms a first i region, a second layer region, and a third layer region. N S
It has a layer structure in which M regions are sequentially formed, and the first layer region and the third layer region are formed sequentially.
The layer region contains more carbon than the second layer region, and when the elemental ratio is expressed as the x value of the composition ratio Si, C, it falls within the range of 0.2 < x < 0.5. The thickness of the first layer region is set to 0.01 to lIJ.
There is provided an electrophotographic photoreceptor characterized in that the thickness of the second layer region is set within the range of 0.05 to 5 μm, and the thickness of the third layer region is set within the range of 10 to 2000 μm.

The present invention will be explained in detail below.

FIG. 1 shows the layer structure of the electrophotographic photoreceptor of the present invention.
According to the figure, a SiC photoconductive layer (2) and an organic photo-semiconductor layer (3) are sequentially laminated on a conductive substrate (1). The a-5iC photoconductive layer (2) has a function of charge generation, and the other organic photoconductive layer (3) has a function of charge transport.

The present invention provides a first layer region (2a), a second layer region (2b) and a third layer region (1i?) as described above inside the a-SiC optical 4D N (2). It is characterized in that the iI region (2c) is sequentially formed, thereby improving photosensitivity, residual potential, and surface potential.

The third one that contains a relatively large amount of carbon! Area 81 (
2c), the difference in dark conductivity between the a-3iC photoconductive layer (2) and the organic photo-semiconductor layer (3) becomes significantly smaller, and thereby both Ji! (2) Carriers are no longer trapped at the interface in (3).

That is, the dark conductivity of the a-SiC photoconductive layer (2) is about 10 days'-10-''(Ω・cw)-', and the dark conductivity of the other organic photoconductive layer (3) is about IQ. -14~10-”
(Ω·CIm) −1, and therefore carriers generated in the a-SiC photoconductive layer (2) cannot smoothly flow to the organic photoconductive layer (3) due to the large difference in dark conductivity.

Therefore, the present inventors formed a third N jI region (2C) with a high content of C element, thereby reducing the dark conductivity of the layer region (2C) and reducing both @ (2) (3) We found that the difference in dark conductivity at the interface can be reduced.

Such a third layer region (2c) is expressed by the C element content ratio and thickness as shown below.

The C element content ratio is 0.2<X with the x value of Si, C,
< 0.5, preferably within the range of 0.3 < If the difference in ratio cannot be made as small as required, and therefore the characteristics of photosensitivity and residual potential cannot be improved, and if the x value is 0.5 or more, the carriers in the a-3iC photoconductive layer It becomes easy to be trapped and the photosensitivity characteristics deteriorate.

Also, the thickness is 10 to 2000, preferably 500 to 10
If the number of people is less than 10, the characteristics of photosensitivity and residual potential cannot be improved.
If there are more than 2,000 people, the residual potential will increase (depending on the amount of injection).

The first layer region (2a) also contains a relatively large amount of carbon, which causes the dark conductivity to be small (so that the carriers of the substrate (1) become a-SiC photo4 photolayer conductive layer). As a result, the surface potential becomes high.

Such a first layer region (2a) is expressed by the C element content ratio and thickness as follows.

The C element content ratio is 0.2 < x value of 5iI-XCX
x<0.5, preferably 0.3<x<0.5
If the x value is less than 0.2, it will not be possible to prevent the injection of carriers from the substrate and increase the charging ability; on the other hand, if the x value is more than 0.5, The residual potential becomes large.

In addition, the thickness is 0.01 to 1 um, preferably 0.05
It is recommended to set it within the range of ~0°5μm<,0.01μm
If it is less than 1 μm, the charging ability cannot be increased, and
If it exceeds this, the residual potential will increase.

The second layer region (2b) is the main photocarrier generating layer of the a-SiC photoconductive N (2), and its element ratio is preferably set within the following range.

The second layer region (2b) is made of amorphous St element and C element, and hydrogen (H) element and halogen element for terminating the dangling bonds of both elements (this terminating element is hereinafter referred to as The compositional formula of these elements is (Si+-x C11).
When expressed as +-y Ay, the X value is 0.05
< x < 0.5, preferably 0.1 < x <
Within the range of 0.4, the y value is 0.1 < V < 0.5
, preferably 0.2×y<0.5, optimally 0.25
It is preferable to set it within the range of < y < 0.45. Excellent light 4 when the X value or y value is set within the above range
Electrical properties and high photosensitivity properties can be obtained.

The thickness of the second layer region (2b) may be set within the range of 0.05 to 5 μm, preferably 0.1 to 3 μm; within this range, high photosensitivity can be obtained and residual potential can be reduced. It gets lower.

Such a first layer region (2a) and a second layer region (2b
) and the third layer region (2c) may be varied in the layer thickness direction. For example, there are examples shown in FIGS. 6 to 1O, in which the horizontal axis is the layer thickness direction, and a is the distance between the first layer region (2a) and the substrate (
1), b is the interface between the first IJR region (2a) and the second layer region (2b), and C is the interface between the second layer region (2b) and the third layer region (2b).
interface of the layer region (2c), d is the third N8N region (2c)
and represents the interface between the organic optical semiconductor layer (3), and the vertical axis represents the C element content.

In addition, when the C element content is changed in the layer thickness direction inside the first layer region (2a), the second layer region (2b), or the third layer region (2c), the C element content The ratio (X value) corresponds to the average content ratio of C element in the entire layer regions (2a), (2b), and (2c), respectively.

The substrate (1) includes a metal conductor such as copper, brass, SUS, or AI, or an insulator such as glass or ceramics coated with a conductor thin film on the surface.
^l is advantageous in terms of cost and adhesion to the a-5iC layer.

Further, the electrophotographic photoreceptor of the present invention is an organic photoconductor N(3).
It can be set to a negatively charged type or a positively charged type by selecting the material. That is, in the case of a negatively charged electrophotographic photoreceptor, an electron-donating compound is selected as the organic photosemiconductor N(3);
In the case of a positively charged electrophotographic photoreceptor, an organic optical semiconductor N(3
) is selected as an electron-withdrawing compound.

Electron-donating compounds include poly-17-
N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensation polymer, etc., and low molecular weight ones include oxadiazole, oxazole, birapurine, triphenylmethane,
These include hydrazone, triarylamine, N-phenylcarbazole, and stilbene.These low-molecular substances include polycarbonate, polyester, methacrylic resin, polyamide, acrylic epoxy, polyethylene, phenol, polyurethane, butyral resin, polyvinyl acetate,
It is used dispersed in a binder such as urea resin.

Electron-withdrawing compounds include 2.4.7-t-linitrofluorene.

Thus, according to the electrophotographic photoreceptor of the present invention, by forming the FJfiI region containing a high content of C element, the photosensitivity and surface potential could be increased, and the residual potential could be reduced.

Further, in the electrophotographic photoreceptor of the present invention, a-5iC
The photoconductive layer (2) contains an element of Group Ma of the periodic table (hereinafter referred to as NLA).
group elements) in an amount of 1 to 500 ppm, preferably 2 to 20 ppm.
It is preferable to contain 0 ppm.

This MA group element content is expressed as an average value for the entire a-SiCJil, and when the average content is 1 ppm or less, the dark conductivity tends to increase, and the photosensitivity decreases. However, 500p
If it exceeds pm, the dark conductivity becomes significantly large, and the ratio of photoconductivity to dark conductivity becomes small, making it difficult to obtain the desired photosensitivity.

When incorporating a Ma group element into the a-SiC photoconductive layer (2), the doping distribution may be either uniform or non-uniform throughout the thickness direction of the FJ. There may be a part of 2) in which there is an HSR region in which the Ma group element is not contained, and in that case, from both the a-SiCP5 region containing the Ma group element and the a-SiC layer region in which the group II element is not contained. Naru a-5iCN
The average content of Ma group elements in the whole is 1 to 500 ppm
Must be.

The MA group elements include B+AI+Ga, In, etc., and B is desirable because it has excellent covalent bonding properties and can sensitively change semiconductor properties, and also because it provides excellent charging ability and photosensitivity.

Next, a method for manufacturing the electrophotographic photoreceptor of the present invention will be described.

To form a-3iCjii, there are thin film forming methods such as glow discharge decomposition method, ion blating method, reactive sputtering method, vacuum evaporation method, and CVO method.

When using the glow discharge decomposition method, Si element-containing gas and C
A film is formed by combining element-containing gases and plasma decomposing the mixed gas. This Si element-containing gas contains 5iHa,
5jzH6+ 5iJa+ 5iFt, 5iC1t
, 5illC1s, etc., and C element-containing gases include CHt, CJa, Czlz, C3H5, etc.
Among these, C211K is desirable in that it can provide high-speed film formation.

The glow discharge decomposition device used in this example will be explained with reference to FIG.

In the figure, the first tank (4), second tank (5), third tank (6), and fourth tank (7) each have 5i11. ,
C211□, BtHh, (3Jb diluted with hydrogen at a concentration of 40 ppm), and H2 are sealed, and these gases are supplied to the corresponding first regulating valve (8), second regulating valve (9),
It is released by opening the 3rd mJi control valve (10) and the 411th valve (11).

The flow rates of the released gases are controlled by mass flow controllers (12), (13), (14), and (15), and each gas is mixed and sent to the main pipe (16).

Note that (17) and (18) are stop valves.

The gas flowing through the main pipe (16) flows into the reaction tube (19), and a capacitively coupled discharge electrode (20) is installed inside this reaction tube (19), and a cylindrical film-forming substrate is also installed. (21) is placed on a substrate support (22), the substrate support (22) is rotationally driven by a motor (23), and the substrate (21) rotates accordingly. Then, the electrode (2
A high frequency power having a frequency of 1 to 50 MHz is applied to 0) and 3, and the substrate (21) is heated to about 200 to 400° C., preferably about 200 to 400° C., by suitable heating means.
It is heated to a temperature of 350°C. In addition, the reaction tube (19) is connected to a rotary pump (24) and a diffusion pump (25), which provide a vacuum state B (gas pressure during discharge of 0.1 to 2 .0 Torr)
can be set.

The substrate (2
When forming an a-SiC layer on 1), the first regulating valve (
8), second regulating valve (9), third regulating valve (lO) and fourth regulating valve
Open the adjustment valve (11) and set SiH++CzHz+Bzll
Release each of the gases a and Ilg, and measure the release amount using a mass flow controller (12) <13) (14) (1
5), each gas is mixed and sent to the main pipe (16
) into the reaction tube (19). Then, when the vacuum state inside the reaction tube, the substrate temperature, and the high-frequency power applied to the electrodes are set to predetermined conditions, a glow discharge occurs, and as the gas decomposes, an a-SiC film containing B element is rapidly spread on the substrate. to form.

After forming the a-5iCPI using the thin film forming method described above, an organic optical semiconductor layer is then formed.

The organic optical semiconductor layer is formed by a dip coating method or a coating method. In the former method, the photosensitive material is immersed in a coating solution in which it is dispersed in a solvent, then pulled up at a constant speed, and then
This method involves natural drying and heat aging (approximately 150°C, approximately 1 hour), and the latter coating method involves applying a photosensitive material dispersed in a solvent using a coater (11). , followed by hot air drying.

〔Example〕

Next, examples of the present invention will be described.

(Example 1) Using the glow discharge decomposition device shown in Fig. 2, 5il14 gas was fed at a flow rate of 200 seconds, and N2 gas was fed at a flow rate of 270 seconds.
With a flow rate of , and c2n, change the gas flow rate, and also change the gas pressure to 0.6 Torr% and the high frequency power to 150 W.
, the substrate temperature was set at 250°C, and a
- A SiC film (film thickness of approximately 1 μm) was formed.

In this way, the carbon content ratio of the a-5iC film was changed, and the amount of carbon in the film was measured by the XMA method.
Further, when the photoconductivity and dark conductivity were measured, the results shown in FIG. 3 were obtained.

In Figure 3, the horizontal axis is the carbon content ratio, i.e., Si, -XC
The vertical axis represents the conductivity, the ○ mark is a plot of photoconductivity for light with an emission wavelength of 550 nm (light intensity 50 μm/cm"), and the mark is a plot of dark conductivity, Moreover, a and b are respective characteristic curves.

Furthermore, when the hydrogen content of each of the above a-SiC films was determined by infrared absorption measurement, the results shown in FIG. 4 were obtained.

In Fig. 4, the horizontal axis is the X value of 5i1-, c, and the vertical axis is the hydrogen content, i.e. (Si+-x CX) +-y
This is the y value of Hy, the ◯ mark is a plot of the amount of hydrogen bonded to the Si atom, the * mark is the plot of the amount of hydrogen bonded to the C atom, and c and d are the respective characteristic curves.

As is clear from FIG. 4, it can be seen that the a-SiC films of this example all have y values within the range of 0.3 to 0.4.

Furthermore, as is clear from Fig. 3, if the carbon content ratio X is within the range of 0.05 < It turns out that is obtained.

(Example 2) Next, in this example, 5il14 gas is pumped at 200sccm.
CzHz gas at a flow rate of 20 sec + s, N
2 gases were introduced at a flow rate of 0 to 101,000 se, and the high frequency power was set to 50 to 300 W and the gas pressure was set to 0.3 to 1.
The a-SiC film (
A film thickness of about 1 μm) was formed.

In this way, various a-SiC films were formed with the carbon content ratio X set to 0.3 and the hydrogen content y varied, and the photoconductivity and dark conductivity of each film were measured. The results shown in the figure were obtained.

In Fig. 5, the horizontal axis is the hydrogen content, that is, the y value of (Si+-xC)I-yH-, and the vertical axis is the conductivity.
The mark indicates the emission wavelength of 550 rv+ (light 1t50 u W/c
Fig. 12 is a plot of photoconductivity against light of m''), . is a plot of dark conductivity, and e and f are respective characteristic curves.

As is clear from Figure 5, when the y value exceeds 0.2,
It can be seen that high photoconductivity as well as low dark conductivity are obtained.

(Example 3) Next, the present inventors developed a-Si film using the film forming conditions shown in Table 1.
C photoconductive N(2) was formed.

[Margin below]

On the a-5iC photoconductive layer thus formed, an organic photoconductor layer (about 15 μm in thickness) made of polycarbonate with a hydrazone compound dispersed therein was formed to obtain an electrophotographic photoreceptor.

When the characteristics of the electrophotographic photoreceptor thus obtained were measured using an electrophotographic property measuring device, it was found that excellent photosensitivity, high surface potential, and low residual potential were obtained.

(Example 4) In forming the first layer region and the third layer region of the electrophotographic photoreceptor of (Example 3), the present inventors used SiH4
By changing the respective flow rates of gas, C211□ gas, and H2 gas, and changing the film formation time,
The X value and thickness of 5il-, C, in each NSM region were changed, and the second layer area was set to be the same as that of the electrophotographic photoreceptor of (Example 3), thus 13 types of electrophotographic photoreceptors were obtained. (Photoreceptors A-M) were manufactured.

Furthermore, when the photosensitivity, residual potential, and surface potential of these photoreceptors were measured, the results shown in Table 2 were obtained.

[Margin below]

In the same table, photosensitivity is classified into three levels based on relative evaluation: ◎, O, and Δ. ◎ indicates the best photosensitivity, and ○ indicates slightly more expensive light. This is the case where sensitivity was obtained, and the Δ mark is the case where the photosensitivity was slightly inferior to the others.

Residual potential is also evaluated relative to three levels; ◎ indicates that the residual potential has decreased, and ○ indicates that the residual potential has decreased somewhat, as is clear from Table 2. , photoconductor D-G and photoconductor J
, M obtained excellent photosensitivity, and moreover, a high surface potential and a reduction in residual potential were observed.

However, the X value of the first layer region of the photoconductors ^ and H is the same as that of the third layer region of the photoconductor L, and the thickness of the third layer region of the photoconductor C is the same as that of the photoconductors B and H. In K, the thickness of the first layer region is different from that of the present invention, and therefore the photosensitivity and
No improvement in residual potential or surface potential was observed.

〔Effect of the invention〕

As described above, according to the electrophotographic photoreceptor of the present invention, a-S
By forming an i region containing a high content of C element inside the iC photoconductive layer, excellent photosensitivity was obtained, and moreover, the surface potential was increased and the residual potential was reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the layer structure of the electrophotographic photoreceptor of the present invention, FIG. 2 is a schematic diagram of a glow discharge decomposition device used in Examples, and FIG. 3 is a line showing the relationship between carbon content and electrical conductivity. 4 is a diagram showing the relationship between carbon content and hydrogen content, FIG. 5 is a diagram showing the relationship between hydrogen content and electrical conductivity, and FIGS. Figure 8, Figure 9 and Figure 1
FIG. 0 is a diagram showing the carbon content in the layer thickness direction of an amorphous silicon carbide photoconductive layer. 1 ・ 2 ・ 2a ・ 2b ・ 2c ・ 3 ・ Conductive substrate amorphous silicon carbide light i'ti first J!
Layer region 2 layer region 3 i region organic optical semiconductor layer patent applicant (663) Kyocera Corporation representative Kinju Anjo Takao Kawamura

Claims (1)

[Claims] In an electrophotographic photoreceptor in which an amorphous silicon carbide photoconductive layer and an organic photoconductive layer are sequentially laminated on a conductive substrate, the amorphous silicon carbide photoconductive layer is provided in a first layer region, a second layer region, and a third layer region. It has a layer structure in which regions are sequentially formed, and the first layer region and the third layer region contain more carbon than the second layer region, and the element ratio is expressed as the x value of the composition ratio Si_1_−_xC_x. , the thickness of the first layer region is 0.01 to 1 μm, the thickness of the second layer region is 0.05 to 5 μm, and The thickness of the layer area is 1
An electrophotographic photoreceptor characterized in that the thickness is set within a range of 0 to 2000 Å.